makecontext.c revision 1.8 
1/*	$NetBSD: makecontext.c,v 1.8 2016/08/10 16:40:24 skrll Exp $	*/
2
3/*-
4 * Copyright (c) 2001 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Klaus Klein.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31
32#include <sys/cdefs.h>
33#if defined(LIBC_SCCS) && !defined(lint)
34__RCSID("$NetBSD: makecontext.c,v 1.8 2016/08/10 16:40:24 skrll Exp $");
35#endif
36
37#include <inttypes.h>
38#include <stddef.h>
39#include <ucontext.h>
40#include "extern.h"
41
42#include <stdarg.h>
43
44void __resumecontext(void) __dead;
45
46void
47makecontext(ucontext_t *ucp, void (*func)(void), int argc, ...)
48{
49	__greg_t *gr = ucp->uc_mcontext.__gregs;
50	__greg_t *sp;
51	int i;
52	va_list ap;
53
54	/* LINTED uintptr_t is safe */
55	sp  = (__greg_t *)
56	    ((uintptr_t)ucp->uc_stack.ss_sp + ucp->uc_stack.ss_size);
57	/* LINTED uintptr_t is safe */
58#if defined(__mips_o32) || defined(__mips_o64)
59	sp -= (argc >= 4 ? argc : 4);	/* Make room for >=4 arguments. */
60	sp  = (__greg_t *)
61	      ((uintptr_t)sp & ~0x7);	/* Align on double-word boundary. */
62#elif defined(__mips_n32) || defined(__mips_n64)
63	sp -= (argc > 8 ? argc - 8 : 0); /* Make room for > 8 arguments. */
64	sp  = (__greg_t *)
65	      ((uintptr_t)sp & ~0xf);	/* Align on quad-word boundary. */
66#endif
67
68	gr[_REG_SP]  = (intptr_t)sp;
69	gr[_REG_RA]  = (intptr_t)__resumecontext;
70	gr[_REG_T9]  = (intptr_t)func;		/* required for .abicalls */
71	gr[_REG_EPC] = (intptr_t)func;
72
73	/* Construct argument list. */
74	va_start(ap, argc);
75#if defined(__mips_o32) || defined(__mips_o64)
76	/* Up to the first four arguments are passed in $a0-3. */
77	for (i = 0; i < argc && i < 4; i++)
78		/* LINTED __greg_t is safe */
79		gr[_REG_A0 + i] = va_arg(ap, __greg_t);
80	/* Pass remaining arguments on the stack above the $a0-3 gap. */
81	sp += i;
82#endif
83#if defined(__mips_n32) || defined(__mips_n64)
84	/* Up to the first 8 arguments are passed in $a0-7. */
85	for (i = 0; i < argc && i < 8; i++)
86		/* LINTED __greg_t is safe */
87		gr[_REG_A0 + i] = va_arg(ap, __greg_t);
88	/* Pass remaining arguments on the stack */
89#endif
90	for (; i < argc; i++)
91		/* LINTED uintptr_t is safe */
92		*sp++ = va_arg(ap, __greg_t);
93	va_end(ap);
94}
95